Re: v7.1b4 bad performance

"Schmidt, Peter" <peter.schmidt@prismedia.com> writes:
> I tried -B 1024 and got roughly the same results (~50 tps).

What were you using before?

> However, when I change WAL option commit_delay from the default of 5
> to 0, I get ~200 tps (which is double what I get with 7.03). I'm not
> sure I want to do this, do I?

Hmm.  There have been several discussions about whether CommitDelay is
a good idea or not.  What happens if you vary it --- try 1 microsecond,
and then various multiples of 1000.  I suspect you may find that there
is no difference in the range 1..10000, then a step, then no change up
to 20000.  In other words, your kernel may be rounding the delay up to
the next multiple of a clock tick, which might be 10 milliseconds.
That would explain a 50-tps limit real well...

BTW, have you tried pgbench with multiple clients (-c) rather than just
one?

            regards, tom lane